While it is anticipated that the use of virtual reality (VR) based simulators, with both visual and haptic (touch) feedback, will significantly improve minimally invasive surgical (MIS) training, leading to substantial reduction in operating room errors and patient morbidity, the current technology is inadequate to address the issues of realistic simulation and rendering in such simulators. The goal of the present project is to improve the realism of simulated MIS procedures by (1) developing novel physically realistic simulation techniques for computing, in real time, the deformation of soft biological tissues with possible nonlinear and viscoelastic material response, incision and cutting as well as the reaction forces on the surgical tools as they interact with the tissue and (2) measuring relevant soft tissue mechanical properties of fresh human cadavers. The starting point of this research is a physics-based computational scheme recently developed, as part of an exploratory (R21) project, as an exciting alternative to the relatively slow performance of finite element- like techniques. A method for enhancing the visual realism of virtual scenes by using video images of actual surgical procedures to render "life like" images during simulations, under development in the exploratory phase, will continue to be pursued. The computational models will be validated by experiments involving the measurement of deformation fields and interaction forces. Experienced MIS surgeons and surgical residents at Harvard Medical School will be involved in evaluating the effectiveness of the simulation technology and the effect of enhanced realism on surgical skill training. Success in this research will establish the technology as a potential standard in next generation surgery simulators due to the ease with which the scheme can be implemented for various MIS procedures. While the particular focus of this project is MIS, the technology developed will be prototypes for a much wider class of medical procedures and accrue benefits outside surgical training, e.g., in the design of new surgical tools and novel surgical techniques. Relevance: The goal of this research is to develop computer-based technology that will vastly improve how surgeons are trained to perform surgery. Better trained surgeons will translate to fewer operating room errors, reduced patient morbidity and improved patient outcomes resulting in faster healing, shorter hospital stay and reduced post surgical complications and treatment costs.